Is it possible to speed up/slow down the preview playback of an animation in the Timeline?
You can use the Time Remapping. Since 2.8, go into Properties &gt; Output &gt; Dimensions &gt; Time Remapping. Previously in Properties &gt; Render &gt; Dimensions:

It expresses the animation speed as a ratio of original speed / new speed, where the speed is expressed in frames. So to reduce the speed 50%, you can use 50/100, 1/2, 100/200 or any other ratio which reduces to 1/2, i.e. 1 frame for every 2 frames.

Note that while frames are used as the units, this setting will interpolate animations on subframes. Not all features support this, see Which animation features don&#39;t support sub-frames? for details.